1. Field of Invention
The present invention relates to a system and method for controlling fuel of gasoline direct injection (GDI) engine.
2. Description of Related Art
In general, a low pressure pump operated by a motor is mounted inside a fuel tank, and a high pressure pump operated by a cam shaft is mounted at a head cover in a fuel system of a gasoline direct injection (GDI) engine.
Further, the fuel system may include an injector for injecting fuel into each combustion chamber, and a pressure sensor for detecting an internal pressure of a fuel rail that is a fuel pressure of each injector.
A fuel of the fuel tank is supplied to the engine by the low pressure pump, and the fuel supplied to the engine is supplied to the fuel rail by the high pressure pump pressurized by about 120 bar.
The pressure sensor which is mounted at the end of the fuel rail detects pressure of the fuel rail and sends the pressure information to a controlling means. The controlling means controls fuel pressure by feedback from the pressure sensor for maintaining optimum pressure of each condition.
A high pressure pump applied to general GDI engine may include a plunger, a control valve, and a solenoid.
In the high pressure pump, the plunger reciprocates up and down with the camshaft and pressurizes a fuel. Further, a compression pressure of fuel is controlled by a closing time of the control valve that is an inlet valve of the high pressure pump when the plunger is in between top dead center and bottom dead center. An outlet valve of the high pressure pump opens when the compression pressure of fuel is reached to a certain pressure, and the fuel moves to the injector.
The controlling means controls discharge rate and discharge pressure of fuel by controlling closing time of the control valve that is an inlet valve of the high pressure pump, since fuel can be discharged when the control valve is fully closed.
The high pressure pump comes to stop within 0.1 seconds when the ignition of the engine is turned off.
The control valve becomes fully open when the high pressure pump stops, therefore a fuel compressed inside the high pressure pump flows backward to the low pressure pump when the high pressure pump stops.
Vibration and noise are created by the pulsation of the fuel flowing backward to the low pressure pump therefore there is a problem that the noise vibration harshness (NVH) is worsening.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.